Observations

If Bullet for a Badman (1964) happened in real history, it would have to happen in or before 1886, since there were never more than two or three hostile warriors at a time after 1886, and there were often no hostile Apache warriors at all during the 13 years from 1873-1886. So if Bullet for a Badman (1964) happened in real history instead of reel history it would happen in or before 1886.

Logan Keliher and Sam Ward were once Texas Rangers.

The Texas Rangers existed in 1823, 1835-1870, and 1873-the present, I think.

Kevin Tate who portrayed Sammy turned 10 in 1964, the year that Bullet for a Badman (1964) was in theaters. Sammy supposedly was so young when his father Sam Ward went to prison that he didn't know Sam was his father and though Logan was his father. So Sam should have stopped being a Texas Ranger and started being an outlaw about 7 to 10 years before Bullet for a Badman (1964).

So Bullet for a Badman (1964) should happen between 1842 to 1880, or between 1880 and 1886, if it happens in the west of real history instead of the Wild West of imagination.

When Sam and Lottie are talking in the shack they talk about going to El Paso like El Paso, at the corner where Mexico, New Mexico, and Texas meet, is the local big city. So that implies that Bullet for a Badman (1964) should happen in west Texas or southern New Mexico.

When the wounded Sam Ward rides away after the bank robbery, a cliff in the background shows a shadowed area that looks like half of a rectangle. It has a short horizontal straight top edge joined at about 90 degrees to to a tall straight vertical right edge. Since straight lines and right angles aren't natural, I assume that someone carved a rectangle, or part of one, out of the cliff face for some reason.

So possibly that rectangular feature has been seen in other movies filmed at that location.

https://www.imdb.com/title/tt0057905/locations?ref_=tt_dt_dt